In this book we define some new methods to approximate a fuzzy function by fuzzy polynomials. Also by introducing some new distances we define the nearest approximations of a fuzzy number. In his book , the definition of fuzzy linear programming with fuzzy variables and a method for solving it according to a special class of ranking which is used to find the approximating polynomials as well as definition of the problem of approximation , are discussed . Then the approximation problem on triangular fuzzy numbers leads us to an approximating polynomial name e -approximation and on the set of all fuzzy numbers , the approximation problem gives us the D-approximation and we present a method to find it , also the universal and SAF-approximations which are special cases of D-approximation are found in this book . Also two best approximations of a triangular valued fuzzy function on a set of points are defined and are computed . Furthermore a chapter contains an idea for computing the nearest approximation of a fuzzy number out of a particular subset of all fuzzy numbers.